POWER LINE COMMUNICATIONS

11/30/2002

Power Line Communication (PLC): PLC allows the use of power grids for data transmission. Power grids represent a ubiquitous and largely unutilized data communication medium that is connected to almost every residence and business in the developed countries.

Power line communication has been used for many years for low speed communications and control. For example, control of street lights.

There are rather significant technical, business and regulatory issues that need to be resolved before power line communications achieves wide scale acceptance. Technical problems include high frequency attenuation, noise, multipath considerations, differing electrical characteristics of different portions of the grid, safety, interference with and by other equipment, etc. both Siemans (1999) and Nortel (2001) have made serious attempts to user power lines for Internet communications and have given up -- primarily because of the large amounts of electrical noise that can be present on the lines. Several demonstration projects with actual customers are in place.

A PLC modem is required to attach devices to the power line.

One current scheme is that the power company acts as an ISP with its base site -- known as an "outdoor master -- at the nearest power substation. Signals are removed from the power lines at that substation and transferred to more conventional media. Intermediate units called "indoor masters" (i.e. routers) concentrate the signals from within a single facility and pass data to/from the modems to the outdoor master. Data rates between 0.8 and 2400 mbit/sec have been demonstrated. Repeaters are required to push signals beyond 300 meters (This is not as easy as it sounds). Experimental deployments at 27 mBit/sec uplink/ 10mbit/sec downlink are expected to a few customers around 4Q2002 or 1Q2003. (This is referred to as a 45mBit/sec system -- and yes, I know that the numbers do not add). These are backbone rates for the whole system, not the rates delivered to the individual customers.

As with cable, wireless, and many other popular technologies power Powerline communications are inherently insecure. It is up to users to prevent neighbors from tapping clear text communications or accessing system resources.

In theory, PLC can be accomplished by conventional ISPs using the power company's resources or by the power company acting as an ISP. In addition, telephone voice services can, in theory, be provided over the power lines.

Within a home (or neighborhood for that matter) individual users can conceivably use their power wiring for communications.

There is an industry association -- the PLCA. It was formed in 2001 to attempt to coordinate standards for powerline communication in North America.

Return To Index Copyright 1994-2002 by Donald Kenney.